Cap screw



Aug- 1, 1950 F. E. FRosT `2,517,476

CAP SCREW Filed July 9, 1945 Mmm ' 2 7a2/672%?? J2 @602% Zjw PatentedAug. 1, `195() UNITED STATES PATENT oi--r-im;v

CAP SCREW Frank E. Frost, Chicago, Ill., assignor of one-half .x il l eThis invention relates to a new and improved cap screw and has forone ofits principal objects the provision of means for causing the cap screwto automatically look when it is screwed up tightly.

Heretofore nuts have been made with integral locking means 'for thepurpose of eliminating separate lock washers. These integral lockingmeans have taken many forms, buteach one of them in some wayrelied onthe binding of the nut threads to cause locking. Caps of screws,however, do not have threads and hence some new means of locking them inLfixed position will be necessary. The need for apap screw lock has onlyrecently been created. Present day cap screws are generally equippedwith socket heads to permit operation of the cap screw when it is in anout of the way position andalso when the cap is to be positioned in arecessed hole to receve the cap or head portion.

Applying separate lock washers to recessed cap screws is a dincult job.The centering of the washer alone takes much time and is very tediouslabor. Lock washers are often lost during assembly or disassembly, andat other times it is almost impossible to remove them from their dirtand grease embedded position.

It is therefore an important object of this invention to provide a lockintegral with a cap screw and which does not rely onthread binding andwhich may be used over and` over again.

Another important object of this invention is the provision of a methodof manufacturing a cap screw having incorporated therein an automaticspring lock to maintain the screw in fixed position.

A still further important object of this invention is to provide asimple, economic and automatically operable cap screw lock which doesnot in any way impair repeated use of the screw and the effectiveness ofthe lock remains constant despite the number of times the screw is used.

Other and further important` objects will become apparent from thedisclosures in the following specication and accompanying drawings inwhich:

Figure 1 is a blank piece of bar stock preferably a malleable ironmaterial.

Figure 2 shows the blank of Figure 1 cut to the general shape of a capscrew.

Figure 3 shows threads cut in the shank and 'a slot cut in the head ofthe cap screw as shown in Figure 2.

Figure 4 shows the lower lip portion of the head bent downwardly.

to Kenneth T. Snow, `Oak lark,`1ll. Application July 9, 1945, serial No.603.874 1 claim. (c1. ismael 2A. Figure `5 shows the cap `screw afterheat hard+ ening treatment applied tothe job `of holding two pieces ofmaterial together. i g

Figure 6 shows the cap screw drawn up tightly in the assembly shown inFigure 5. i e

Figure 7 is a top plan` view of the cap screw of this invention. I I IFigure 8 is a sectional view taken on the line -ofFiguret 1, 1` e Asshown in the drawings: The first four iig--l ures of the drawingprogressively show the steps in the manufacture of the cap screwof` thisin* vention. The reference` numeral I0.. indicates generally a bar ofstandard steel iromwhich the cap screw of this invention is made. Figure.2' shows the bar I0 cut or formed to include` an enlarged head portionI I and a depending shank portion I2. Figure 3 has had threads I3 cut inthe lower portion of the shank I2.` A. slot Il preferably parallel tothe top and bottom of the head I I is cut radially inwardly and as shownin Figure 8 is defined by a chord I5 and its included arc IG. The chordI5 is located outside the circumference of the shank portion I2. Howeverthe slot may be made at any angle with respect to the top of the headand the desired locking effect could still be secured. The inner edge ofthe slot need notrbe a straight chord but might well take the form of anarc. It is preferable that the slot I 4 be located in the lower portionof the head I I.

A hexagonal socket I'I as shown in Figure '7 is cut axially of the capscrew in the head II for the purpose of turning the screw. It should beunderstood that the shape of the socket II may be varied or may even bedispensed with if the head is provided with some other means tofacilitate turning such as a polygonal outer periphery. In the desiredform the head I I, as shown, is cylindrical for convenient recessing ofthe heads when the screws are in use and it is desired to have acontinuously smooth surface.

A thin lower 11p la formed by the 'slot u is' bent downwardly as shownin Figure 4. In this condition the entire cap screw is hardened byproper heat treatment to cause the screw to withstand great stresses andstrains, and also to cause the lip I8 to possess spring characteristics.The spring lip I8 will hereafter tend to resume its curved down shapeand this tendency is utilized in effecting a lock for the cap screw.

In Figure 5 the finished, hardened cap screw is shown as assembling theplate I9 to an inner piece of material 2D. The piece of material 20 hasan internally threaded bore 2| adapted to receive the threaded shankportion I3 of the cap screw. The plate I9 is equipped with a bore 22 ofslightly larger diameter than the shank l2 of the screw but of lessdiameter than the head Il of the screw. An enlarged recess 23 isprovided pushed upwardly as shown in Figure 6, but inasmuch as the lipis now normally tending toward a downward position it exerts anincreased vforce at its area of contact with the shoulder 25. Thisincreased force acts as a lock against unwarranted rotation of thescrew.

Numerous details o f` construction could be varied without departingfrom the principles of thecap'screwlockdisclosed herein, and Ithereforedo not propose limiting the patent granted hereon otherwise than asnecessitated by the appended claim.

I claim: y ""Acap'screw comprising a cylindrical threaded shank,lacylindrical head for said shank of greater diameterthan said shank andintegral with said shank and concentrically disposed at the upper endthereof, said head having a flat annular undersideat right angles tosaid shank, said head havinga socket in the top thereof for engagementbya turning tool, said head having a single trans- Yerse'ly vdisposedslot in the side of the head, said slot dened by a chord located acrosssaid head Further downward movement of the screw will cause the lip tobei locking of the cap screw.

4 outside the circumference of the shank and the lesser part of the headcircumference included in said chord, and said slot disposed in a lowerportion of said head defining a relatively thin lower lip and retaininga large thick head, said thin lower lip curved downwardly andpossessingy springVA characteristics vwhereby when the cap `screwfisdrawn up against a relatively flat surface the thin lower lip springsupwardly against the head causing an automatic spring FRANK E. FROST.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

